How To Build An AR-15 (The Complete Parts Guide)

We've got a lot to cover, so we'll keep this short: You want to build an AR-15 from scratch. You might have no idea where to begin. We're going to teach you everything you need to know! The rifle we're piecing together in this guide is a typical AR-15 with a 16" barrel, chambered in 5.56/.223. That's the gold standard for nearly all rifles (the beauty is, you can customize later). First, we'll look at the relevant gun laws and answer some questions you probably have. Next, we'll explain every part you need to build your own AR-15 kit, including which parts are best for a well-rounded, affordable rifle. Lastly, we'll go over the different types of ARs and calibers you can build (a rifle, pistol, or a short-barreled rifle/SBR).

Let's begin! You probably have questions, so we answered the most common ones:

AR-15 build FAQs

Q: Is it legal to build my own AR-15 at home?

A: Yes, with some restrictions. The ATF has long held that it's 100% legal to build your own AR-15 (and most guns) at home for personal use. You need special paperwork to build a short-barreled rifle (SBR), which is considered an NFA item. We don't need to worry about that right now, we're building a regular rifle.

Q: Do I need an FFL or background check?

A: That depends. If you build your AR-15 using a stripped lower receiver, you'll need to go through an FFL, fill out some paperwork, and conduct a background check. If you're building your rifle or pistol using an 80% lower receiver, you don't need to any of that in most states. Some states require it, like California. Check your local and state laws before building.

For a quick guide on building your AR-15 in California, click here.

Q: Does my AR-15 need a serial number?

A: That also depends. If you buy a stripped lower receiver, it'll have a serial number for paperwork and your background check. 80% lowers do not need a serial number under federal law. The ATF doesn't require a serial number for homemade firearms made for personal use, but some states do. Again, check your local and state laws on this one.

Q: What is an 80% lower receiver?

A: An 80% lower receiver is a firearm blank. You can use one to build your AR-15 at home, and it's what we specialize in. For a complete guide and FAQ on 80% lowers, click here.

If you have more questions about building before getting started, just email or call us. We're happy to help. We'll even get the guy who wrote this guide to help you out, if needed.

The Full AR-15 Parts List

The AR-15, regardless of configuration or caliber, can be separated into two major components: The upper receiver assembly, and the lower receiver assembly. You'll need to do some assembly and fitting with parts on the lower receiver, but let's break down all the parts contained in each half, first:

Upper Receiver Parts You'll Need

• Barrel
• Gas tube
• Gas block
• Hand guard
• Charging handle
• Bolt carrier group
• Stripped upper receiver

Most barreled upper receivers, like those included with our own build kits, ship preassembled and ready to fire. To make it easy, you can grab one with everything assembled and configured correctly.